[PATCH] cpu: Check blockers in virCPUCompareUnusable only if they exist

[Jiri Denemark <jdenemar@xxxxxxxxxx>]

virCPUCompareUnusable can be called with blockers == NULL in case the
CPU model itself is usable (i.e., QEMU reports an empty list of
blockers), but the CPU definition contains some additional features
which have to be checked.

Fixes: v10.8.0-129-g5f8abbb7d0
Reported-by: Han Han <hhan@xxxxxxxxxx>
Signed-off-by: Jiri Denemark <jdenemar@xxxxxxxxxx>
---
 src/cpu/cpu.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/src/cpu/cpu.c b/src/cpu/cpu.c
index 2b0d641e78..58fba3781c 100644
--- a/src/cpu/cpu.c
+++ b/src/cpu/cpu.c
@@ -201,11 +201,13 @@ virCPUCompareUnusable(virArch arch,
     char **blocker;
     size_t i;
 
-    for (blocker = blockers; *blocker; blocker++) {
-        if (!(feat = virCPUDefFindFeature(cpu, *blocker)) ||
-            feat->policy != VIR_CPU_FEATURE_DISABLE) {
-            virBufferAddStr(&features, *blocker);
-            virBufferAddLit(&features, ", ");
+    if (blockers) {
+        for (blocker = blockers; *blocker; blocker++) {
+            if (!(feat = virCPUDefFindFeature(cpu, *blocker)) ||
+                feat->policy != VIR_CPU_FEATURE_DISABLE) {
+                virBufferAddStr(&features, *blocker);
+                virBufferAddLit(&features, ", ");
+            }
         }
     }
 
-- 
2.47.0